Prior art in this area started with the advent of digitizing scanners. Once documents could be scanned into digital data format, scaling could be performed algorithmically in hardware or software. Many algorithms have been devised with respect to this topic, virtually all requiring significant amounts of data processing throughput. Because of high throughput requirements and advances in semiconductor technology, more of these algorithms are being realized in digital hardware implementations.
A patent of interest for its teachings in this art area is U.S. Pat. No. 4,275,450 entitled "Magnification/Demagnification Apparatus and Method" by J. L. Potter. The patent discloses an apparatus and a method which permits the selective variation in the size of an output image derived from digital image signals. The apparatus performs a reduction by generating a reduction count which count is used to control the gating of a series of image pixels such that the pixel existing at the input to a gate at the time the count is reached is not passed. The reduction count is continually cycled such that the pixels occurring at the input to the gate at the time of the count being reached are inhibited. The process of multiplication, or of increasing the size of the image, is accomplished by passing the pixel on the input of the gate more than once. For example, if the image is to be doubled in size two pixels will be passed for each pixel received.
The to be scaled image data may be taken directly from a scanner, scaled, and processed results sent to an output device. However, this is not widely done because of mismatches in throughput and dependencies on scale factors. The scanned image data is normally stored in a frame buffer memory and retrieved under direct memory access, programmed input/output, or interrupt driven input/output control. The processed (scaled) image data may then be stored in a system memory. It would be desirable to have a scaling system and method that could also accept data from a compression/expansion processor based upon the CCITT document standard. This allows documents that were previously scanned, compressed and stored on disk to be retrieved, expanded and scaled.